Sleeping more than eight hours ‘increases stroke risk’

London – People who sleep for more than eight hours a day are more likely to have a stroke, research has shown – but experts do not know why.

A study of nearly 10 000 people carried out at the University of Cambridge found that those who slept eight hours on average had a 46 per cent higher than average risk of having a stroke.

Adults tend to need between six and nine hours' sleep, but oversleeping has previously been linked with health problems such as diabetes.

However, it was unclear from this latest study whether sleeping for more than eight hours was actually causing problems that can lead to stroke, or if it was merely an indicator of underlying conditions.

Lack of sleep has been linked with disruptions to the body's metabolism and can also raise the levels of the so-called “stress hormone” cortisol, both of which could lead to higher blood pressure and raise the likelihood of stroke. Why too much sleep could have a similar outcome remains a mystery.

Dr Madina Kara, research manager at the Stroke Association, said the study, published in the journal Neurology, did not amount to evidence that too much sleep led to a stroke.